<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>level 1</title>
</head>
<body>
level 1
请输入答案：
<input type="text" id="in"><button onclick="check()">提交</button>
<script>
  function check(){
    var ui=document.getElementById('in').value;
    if(ui=='答案')window.open("l2.html");
    else alert('错误');
  }
</script>
</body>
</html>